Method of making a photographic base material

ABSTRACT

A METHOD OF MAKING A PHOTOGRAPHIC BASE MATERIAL HAVING SUITABLE ADHESIVE PROPERTIES WITH RESPECT TO A SUBSEQUENTLY-APPLIED PHOTOGRAPHIC LIGHT-SENSITIVE EMULSION, SAID METHOD COMPRISING APPLYING TO A SUBSTRATE OF POLYETHYLENE FILM OR A POLYETHYLENE-COATED PAPER A MEMBER SELECTED FROM THE GROUP CONSISTING OF A FIRST MATERIAL HAVING SUITABLE ADHESIVE PROPERTIES WITH RESPECT TO A SUBSEQUENTLY-APPLIED LIGHT-SENSITIVE EMULSION AND A SECOND MATERIAL HAVING SUITABLE ADHESIVE PROPERTIES WITH RESPECT TO A SUBSEQUENTLY-APPLIED LIGHT-SENSITIVE EMULSION AFTER BEING SUBJECTED TO AN ELECTRICAL DISCHARGE TREATMENT TO A DRY THICKNESS OF FROM 0.5 TO 3 MICRONS, DRYING THE RESULTING COATING TO A WATER CONTENT OF FROM 5 TO 30%, BY WEIGHT, BASED ON THE TOTAL WEIGHT OF THE COATING AND SUBJECTING THE RESULTING COATED SUBSTRATE TO A CORONA DISCHARGE TREATMENT.

United States Patent @fice 3,669,709 Patented June 13, 1972 3,669,709 METHOD OF MAKING A PHOTOGRAPHIC BASE MATERIAL Tsuneo Kasugai and Nobuhiko Minagawa, Shizuoka,

Japan, assignors to Fuji Photo Film Co., Ltd., Kauagawa, Japan No Drawing. Filed June 1, 1970, Ser. No. 42,515 Claims priority, application Japan, May 31, 1969, 44/ 42,801 Int. Cl. B44d 1/44 US. Cl. 11734 10 Claims ABSTRACT OF THE DISCLOSURE A method of making a photographic base material having suitable adhesive properties with respect to a subsequently-applied photographic light-sensitive emulsion, said method comprising applying to a substrate of polyethylene film or a polyethylene-coated paper a member selected from the group consisting of a first material having suitable adhesive properties with respect to a subsequently-applied light-sensitive emulsion and a second material having suitable adhesive properties with respect to a subsequently-applied light-sensitive emulsion after being subjected to an electrical discharge treatment to a dry thickness of from 0.5 to 3 microns, drying the resulting coating to a Water content of from 5 to 30%, by weight, based on the total weight of the coating and subjecting the resulting coated substrate to a corona discharge treatment.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a method of making a photographic base material and more particularly, it is concerned with a method of making a ph0t0graphic base material consisting of a polyethylene film or a polyethylene-laminated paper wherein its adhesiveness to a lightsensitive emulsion is improved.

(2) Description of the prior art As is well known, the surface of polyethylene has a poor adhesive property to other materials. Therefore, when a light-sensitive emulsion containing gelatin as a binder is coated onto a base material having a polyethylene surface, the adhesion between the light-sensitive emulsion layer and the base material is not sufficient, often resulting in peeling of the light-sensitive emulsion layer during drying or developing. Such a light-sensitive material has thus not been in practical use.

It is disclosed in British Patent No. 971,058 that an electron bombardment, such as a corona discharge, may be employed to improve the adhesiveness of a light-sensitive emulsion layer to a polyethylene surface. In this method, the polyethylene surface is directly subjected to a corona discharge treatment to make it hydrophilic, whereby the adhesiveness is improved. This method is very effective but, on the contrary, has the disadvantage that the effect of the discharge treatment is partially or completely lost, for example, by friction over a period of time from the discharge treatment to the coating of a light-sensitive emulsion layer, since the change in the polyethylene surface caused by the discharge treatment is relatively slight and the mechanical strength thereof is not sufiicient. Furthermore, the polyethylene surface is so sensitive to electrostatic charge that it attracts ambient dust, resultsulting in deterioration of the adhesion improving effect.

SUMMARY OF THE INVENTION The present invention solves the above problems and in accordance with the present invention, there is provided a method of making a photographic base material which comprises applying either (a) a material having a good adhesive property with respect to a light-sensitive emulsion layer, or (b) one having a good adhesive property to a light-sensitive emulsion layer after a corona discharge treatment, to a polyethylene film or a polyethylene surface of a polyethylene-laminated paper in a dry thickness of 0.5 to 3 microns to produce a coated layer, drying the coated layer until the water content thereof is reduced to 5 to 30%, by weight, and then subjecting the surface of the coated layer to corona discharge treatment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The corona discharge treatment is not carried out directly on the polyethylene surface, but instead is performed after the coating of the polyethylene surface with the coated layer, whereby the adhesive property of the film (coated layer) provided on the polyethylene surface is improved.

As the above-mentioned materials having a good adhesive property to the light-sensitive emulsion layer, there may be illustrated: water-soluble or alkaline Water-soluble natural high molecular weight materials such as gelatin and casein. As the material showing a good adhesive property to the 1ight-sensitive emulsion after a corona discharge treatment, there may be illustrated: water-soluble high molecular weight materials such as polyvinyl alcohol, starch, acrylamide or hydrosols of acrylic acid esters.

Coating of the foregoing materials onto the polyethylene surface without a discharge treatment can be carried out by using a conventional bar coating method or gravure coating method, but in order to obtain a uniform coating at high speeds, a material which improves the wetting of the polyethylene surface may be added to the polyethylene or the polyethylene may be subjected to a brief corona discharge or gas flame treatment, 'within the scope of the present invention.

The discharge treatment after the coated layer is ap plied must be carried out after drying the coated layer to a water content of from 5% to 30%. In cases where the water content exceeds this range, the effect of the discharge treatment hardly reaches the interface between the polyethylene bottom layer and the coated layer; while, in cases where the water content is less than 5%, it is difiicult to obtain a sufficient adhesion elfect.

The thickness of the coated layer depends somewhat on the quality thereof and preferably varies from 0.5 to 3 microns on a dry base. The reason for this limitation is, as is evident from the foregoing illustration, that a thickness of less than 0.5 micron cannot give a sufiicient mechanical strength nor protecting action, while that of more than 3 microns hinders the efliect of the discharge treatment, i.e., prevents it from reaching the polyethylene surface.

In the method of the present invention, a polyethylene surface is first coated with a film which is adhesive to a light-sensitive emulsion or rendered adhesive by a discharge treatment, and then the assembly is subjected to a high voltage electric stress with discharge through the coating, thereby enhancing the adhesiveness of the coating to the polyethylene surface. A photographic base material obtained by this method has an excellent stability with the passage of time, even until a light-sensitive emulsion is coated thereon, as well as having a high mechanical strength. In addition, the material is not sensitive to electrostatic charge. Moreover, its adhesiveness to the lightsensitive emulsion layer is suflicient for practical applications.

The following examples are provided to illustrate the present invention further in detail without being intended to limit the same in any way.

Example I.-A dry base polyethylene laminated paper, made by extruding polyethylene having a density of 0.92 in a thickness of about 30 microns to both sides of a photographic raw base paper of 150 g./m. was coated with a 10% gelatin solution to a thickness of 1 micron by the use of a commercially sold, wire wound coating rod, dried by air until the Water content of the resulting gelatin film was 20% and then subjected to a discharge treatment using a corona discharge apparatus (made by Lepel Co.) having movable electrodes provided in parallel with a sample at an interval of 0.8 mm. therefrom at a discharge electric power of 200 W. (length of electrode 20 cm.) and an electrode moving speed of 10 mJmin.

The thus obtained sample was coated with an ordinary photographic light-sensitive emulsion, dried and developed. No peeling of the coating occurred. The adhesiveness of the resulting photographic paper was suflicient for practical use. Employing the same polyethylene laminated paper not subjected to the treatment of the present invention, however, the emulsion film was partially peeled oif during development.

When a base material subjected to the treatment of the present invention and another base mate 'al subjected directly to a corona discharge treatment &520 w. (without coating the foregoing protective layer reon) were allowed to stand in a room for 50 days, coated with a photographic light-sensitive emulsion as described above, dried and developed, the former held its adhesiveness but the latter showed a peeling of the edges of the coating during the development.

The adhesive force of the polyethylene to the emulsion'film before and after the passage of time was measured, about the same samples before development to obtain the results tabulated below.

The measurement'was carried out by bonding a cellulose triacetate film (100 microns) to the emulsion surface with the use of suitable adhesives (Araldite, Ciba Ltd.), allowing the assembly to stand at 30 C. for 48 hours to thereby harden the adhesives, partially peeling one end of the aflixed film strip by hand, fixing the the peeled ends of the film sample strip to the opposite clamps of a Schoppers Tensile Strength Tester, the sample strip being cut to a width of mm., and then measuring the stripping strength.

It is clear from the above results that the method of the present invention produces a base material having excellent durability compared with a material subject to a direct corona discharge treatment without having the benefit of the protective coating of the present invention.

Example II.A T-die extrusion film of medium pressure method polyethylene having a thickness of 100 microns, as a base material, was coated with a 10% sodium polyacrylate solution to a thickness of 2 g./m. on a dry base, dried until the water content of the coating was 8% and then subjected to a corona discharge in a manner similar to that of Example I.

The surface resistance of the thus obtained film was 10 -10 0 and less than 10 -10 9 in the case of a direct corona discharge treatment only. The electrostatic adhesion of dust was markedly reduced.

A light-sensitive material obtained by coating the resulting film with a silver iodobromide photographic emulsion showed a suflicient adhesiveness for practical applications.

Example III.Both surfaces of an original paper having a StiSckigt size of 400 seconds or more, a width of 50 cm. and a density of 200 g./m. were coated with a high pressure method polyethylene containing 0.2 parts of an amphoteric surfactant (AMS 313, made by Lion Yushi K.K.), to a thickness of 40 micron (per side) and the polyethylene surface was subsequently coated with a hydrosol of polybutyl acrylate obtained by emulsion polymerization to give a thickness of 0.5 microns, on a dry base. The coating was continuously carried out at a rate of 30 m./min. by use of a gravure coater. The coated film was dried in a channel drier until the water content of the coated layer was 1015% and then subjected to a discharge treatment of 300 w. while maintaining the distance between the sample and the electrode at 1.0 mm. by means of a corona discharge apparatus previously set to a point on the film having such a water content.

About the thus obtained sample A, the original polyethylene laminated paper B and a polyethylene laminated paper C subjected to a direct corona discharge treatment only, the adhesive force to a photographic light-sensitive emulsion, coated thereon and dried, was measured by the method of Example I after the time period indicated below to give the results tabulated below.

What is claimed is:

1. A method of making a photographic base material having suitable adhesive properties with respect to a subsequently-applied photographic light-sensitive emulsion, said method comprising applying to a substrate of polyethylene film or a polyethylene-coated paper an aqueous composition consisting of a first material having adhesive properties with respect to a subsequently-applied lightsensitive emulsion or to a second material having adhesive properties with respect to a subsequently-applied lightsensitive emulsion after being subjected to an electrical discharge treatment, to a dry thickness of from 0.5 to 3 microns, drying the resulting coating to a water content of from 5 to 30%, by weight, based on the total weight of the coating and subjecting the resulting coated substrate to a corona discharge treatment in a non-reactive atmosphere.

2. The method as in claim 1, wherein said first material is gelatin or casein.

3. The method as in claim 1, wherein said second material is selected from the group consisting of polyvinyl alcohol, starch, acrylamide and hydrosol of an acrylic acid ester.

4. A method for making a photographic base material having suitable adhesive properties with respect to a subsequently-applied photographic light-sensitive emulsion, said method comprising applying to a substrate of polyethylene film or a polyethylene-coated paper, an aqueous composition consisting of a first material having adhesive properties with respect to a subsequently-applied lightsensitive emulsion, said first material being a water-soluble or alkaline water-soluble natural high molecular weight material, or to a second material having adhesive proper ties with respect to a subsequently-applied light-sensitive emulsion after being subjected to an electrical discharge treatment, to a dry thickness of from 0.5 to 3.0 microns, said second material being a water-soluble high molecular weight material, drying the resulting coating to a water content of from 5.0 to 30.0%, by weight, based on the total weight of the coating, and subjecting the resulting coated substrate to a corona discharge treatment in a non-reactive atmosphere.

5. A method of making a photographic base material having suitable adhesive properties with respect to a subsequently-applied photographic light-sensitive emulsion,

said method comprising applying to a substrate of polyethylene film or a polyethylene-coated paper, an aqueous composition consisting of a first material having adhesive properties with respect to' a subsequently-applied lightsensitive emulsion, said first material being a member selected from the group consisting of casein and gelatin, or to a second material having adhesive properties with respect to a subsequently-applied light-sensitive emulsion after being subjected to an electrical discharge treatment, to a dry thickness of from 0.5 to 3.0 microns, said second material being a member selected from the group consisting of polyvinyl alcohol, starch, acrylamide and a hydrosol of an acrylic acid ester, drying the resulting coating to a Water content of from 5.0 to 30.0%, by weight, based on the total weight of the coating, and subjecting the resulting coated substrate to a corona discharge treatment.

6. A method of claim 1, further comprising the step of coating a light-sensitive photographic emulsion onto the thus prepared base material.

7. The method of claim 4, further comprising the step of coating a light-sensitive photographic emulsion onto the thus prepared base material.

8. A method of claim 5, further comprising the step of coating 2. light-sensitive photographic emulsion onto the thus prepared base material.

9. A method of making a photographic base material having suitable adhesive properties with respect to a subsequently-applied photographic light-sensitive emulsion, said method comprising applying to a substrate of polyethylene film or a polyethylene-coated paper, an aqueous composition consisting of a first material having adhesive properties with respect to a subsequently-applied lightsensitive emulsion, said first material being a member selected from the group consisting of casein and gelatin, or to a second material having adhesive properties with respect to a subsequentlyapplied light-sensitive emulsion after being subjected to an electrical discharge treatment, to a dry thickness of from 0.5 to 3.0 micron, said second material being a member selected from the group consisting of polyvinyl alcohol and starch, drying the resulting coating to a water content of from 5.0 to 30.0% by weight, based on the total weight of the coating, and subjecting the resulting coated substrate to a corona discharge treat ment.

10. The method of claim 9, further comprising the step of applying a light-sensitive photographic emulsion onto the thus prepared base material.

References Cited UNITED STATES PATENTS 3,424,735 1/ 1969 Bucheister et a1. 117-93.1 CD

ALFRED L. LEAVITI, Primary Examiner J. H. NEWSOME, Assistant Examiner US. Cl. X.R.

ll7--93.l CD, 138.8 E; 204- 

